Clean good water. Gives your kribs cave and such. And you should try and get sand or gravel that the kribs are able to dig under rocks and make their own cave. A lot of people say to put a flower pot in upside down with a little door cut in the side. Kribs like a smooth area to lay the eggs on and will not lay eggs in the open like other dwarf cichlids. The cave should only basically have one entrance but the little hole at the bottom of a pot should be ok. Although I have never used one yet.
The first picture they are hiding in the plant but you can see one off to the right a bit. In the other two photos they are resting on the rock.